The present invention relates to an inkjet recording apparatus, and more particularly, to an inkjet recording apparatus for printing on a long product such as a cable.
An inkjet recording apparatus is configured to print by subjecting an ink injected from a nozzle to particulation at a constant cycle, and performing electrical charging and polarization at an optimum timing in the particulation in accordance with print information.
Generally, as disclosed in Patent Document 1 (JP-A No. 2011-46139), the lag in timing for charging of the ink particle may deteriorate printing quality. For the purpose of detecting the optimum timing for charging, the particulation cycle is divided into N phases, and charging is performed while shifting the phase by 1/N while preventing polarization of the ink particle so as to detect the optimum charging phase based on the respective charged amounts. As the misalignment of the optimum charging phase is likely to be influenced by the change in the ink injection pressure, ambient temperature and the like, the optimum charging phase is detected during a non-printing period between printing periods.
A printing speed, that is, a high frequency printing performance is one of indicators that represent performance of the inkjet recording apparatus. There has been introduced a method for increasing the printing speed by reducing non-printing period at an interval between the printing operations. In the interval between the printing operations, the process for detection of the optimum charging phase, and calculation of the charged amount in accordance with print information charged to the ink particle is executed. The process for detection of the optimum charging phase takes up about half the time for the non-printing period between the printing operations. The aforementioned printing method only for the single printing object fails to cope with printing on a long product such as the cable, hose, and pipe.
A generally employed inkjet recording apparatus for printing on a single product executes detection of the optimum charging phase, and calculation of the charged amount in accordance with the print information charged to the ink particle in the interval between printing operations. However, the apparatus is not capable of executing printing on such a long product as the cable, hose and pipe in the optimum charged state. A charging signal of the inkjet recording apparatus will be described hereinafter.
The inkjet recording apparatus allows a charging electrode to apply two kinds of charging signals to the ink particles, that is, a printing charging signal that charges the ink particle for formation of character information to be printed, and a phase detection charging signal that charges the ink particle so as to detect the optimum charging timing.
The inkjet recording apparatus is required to apply the printing charging signal to the ink particle at the optimum charging timing constantly. If the printing charging signal is applied to the ink particle at an inappropriate charging timing, print disorder may occur. Furthermore, the optimum charging timing changes from time to time owing to a plurality of factors, for example, viscosity or temperature of the ink. Therefore, it is necessary to detect the change in the optimum charging timing by constantly applying the phase detection charging signal to the ink particles when the printing is not performed (the printing charging signal is not generated) so as to follow-up the detected change.
A method of detecting an optimum charging timing executed by a generally employed inkjet recording apparatus will be described referring to FIGS. 6A and 6B. Referring to FIG. 6A, (a) represents a sensor signal for detection of a non-printing object, and (b) represents detection of the optimum printing timing performed by applying the phase detection charging signal which exists between the print information (printing charging signal) and the next print information (printing charging signal) to the ink particle during the non-printing period.
With the application of infinite printing with continuous print information (printing continuously performed on the surface of the long product with the length ranging from several to several tens meters, for example, the cable, hose and pipe will be referred to as the infinite printing), there is no time interval between the print information data. It is therefore impossible for the generally employed control method to apply the phase detection charging signal to the ink particle as shown in FIG. 6B, and to detect the optimum printing timing.
It is an object of the present invention to constantly detect the optimum charging timing for the infinite printing application of printing on the surface of the long product such as the cable, hose and pipe so as not to cause the print disorder.